Luminescent Carbon Dots from Wet Olive Pomace: Structural Insights, Photophysical Properties and Cytotoxicity.

Carbon nanomaterials endowed with significant luminescence have been synthesized for the first time from an abundant, highly localized waste, the wet pomace (WP), a semi-solid by-product of industrial olive oil production. Synthetic efforts were undertaken to outshine the photoluminescence (PL) of carbon nanoparticles through a systematic search of the best reaction conditions to convert the waste biomass, mainly consisting in holocellulose, lignin and proteins, into carbon dots (CDs) by hydrothermal carbonization processes. Blue-emitting CDs with high fluorescence quantum yields were obtained. Using a comprehensive set of spectroscopic tools (FTIR, Raman, XPS, and 1H/13C NMR) in combination with steady-state and time-resolved fluorescence spectroscopy, a rational depiction of WP-CDs structures and their PL properties was reached. WP-CDs show the up-conversion of PL capabilities and negligible cytotoxicity against two mammalian cell lines (L929 and HeLa). Both properties are excellent indicators for their prospective application in biological imaging, biosensing, and dynamic therapies driven by light.

Spectroscopic Analysis of Parathyroid and Thyroid Tissues by Ground-State diffuse Reflectance and Laser Induced Luminescence: a Preliminary Report.

Intraoperative discrimination of thyroid and parathyroid tissues is fundamental in thyroid surgery. Recent fluorescence studies have shown stronger NIR emission in parathyroid tissue than in thyroid tissue, presenting a potential avenue for the development of a tool for surgical assistance. However, the fluorophore responsible for this emission has not yet been identified. In this work, spectroscopic analysis was performed to ascertain the origin of the emission peaks in parathyroid tissue. Ground-state diffuse reflectance (GSDR) absorption spectroscopy and laser-induced luminescence (LIL) emission spectroscopy were performed in parathyroid, thyroid, and fatty tissue samples and the resulting spectra were compared with the peaks of known fluorophores to identify the origin of each peak. The spectra of the different tissue types were also compared in order to evaluate the wavelength which presents the highest parathyroid emission relative to the emission of the surrounding tissues, representing the ideal wavelength for parathyroid detection. An emission peak in these conditions was observed for both thyroid and parathyroid tissue at 711 nm, with a higher intensity in parathyroid sample, making it suitable for detection applications. These results show a potential avenue for the development of a system allowing parathyroid detection in a surgical setting.

Versatility of Amide-Functionalized Co(II) and Ni(II) Coordination Polymers: From Thermochromic-Triggered Structural Transformations to Supercapacitors and Electrocatalysts for Water Splitting.

The new 2D coordination polymers (CPs) [M(L)2(H2O)2]n [M = CoII (1) and NiII (2); L = 4-(pyridin-3-ylcarbamoyl)benzoate] were synthesized from pyridyl amide-functionalized benzoic acid (HL). They were characterized by elemental, Fourier transform infrared, thermogravimetric, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction (XRD) structural analyses. Single-crystal XRD analysis revealed the presence of a 2D polymeric architecture, and topological analyses disclose a 2,4-connected binodal net. A thermochromic effect leads to the production of two new CPs, 1' and 2', by heating at ca. 220 °C, accompanied by a color change from orange to purple in the case of 1 and from blue to green in the case of 2. The transformation of 1 to 1' takes place through an intermediate (1a) with a different twist of the L- ligand, leading to the formation of a 1D polymeric architecture, as proven by single-crystal XRD analysis. The addition of water or keeping 1' or 2' in air for several days leads to regeneration of 1 or 2, respectively. The thermochromic-triggered structural transformations of 1 and 2 were further substantiated by PXRD and UV-vis ground-state diffuse-reflectance absorption studies. The supercapacitance ability of the CPs 1 and 2 and a Ni-Co composite (made from mixing the CPs 1 and 2) was investigated by electroanalytical techniques, such as cyclic voltammetry and electrochemical impedance spectroscopy. The CP 2 exhibits the highest specific capacity of 273.8 C g-1 at an applied current density of 1.5 A g-1. These newly developed CPs further act as electrocatalysts for the water-splitting reaction.

Synthesis, Photochemical and In Vitro Cytotoxic Evaluation of New Iodinated Aminosquaraines as Potential Sensitizers for Photodynamic Therapy.

In this work, several benzothiazole-based aminosquaraine dyes, displaying strong absorption within the so-called phototherapeutic window (650⁻800 nm), were synthesized. The ability, of all the new dyes, to generate singlet oxygen was assessed by determining the correspondent phosphorescence emission and through the comparison with a standard. The quantum yields of singlet oxygen generation were determined and exhibited to be strongly dependent on the nature of the amino substituents introduced in the squaric ring. The photodynamic activity of the synthesized dyes was tested against four human tumor cell lines: breast (MCF-7), lung (NCI-H460), cervical (HeLa) and hepatocellular (HepG2) carcinomas; and a non-tumor porcine liver primary cell culture (PLP2). All the compounds synthesized were found to be able to inhibit tumor cells growth upon irradiation more than in the dark, in most of the cases, very significantly. Considering the photodynamic activity exhibited and the low toxicity displayed for the non-tumor cells, some of the synthetized dyes can be regarded as potential candidates as photosensitizers for PDT.

Synthesis, spectroscopic characterization and biological evaluation of unsymmetrical aminosquarylium cyanine dyes.

New unsymmetrical aminosquarylium cyanine dyes were synthesized and their potential as photosensitizers evaluated. New dyes, derived from benzothiazole and quinoline, were prepared by nucleophilic substitution of the corresponding O-methylated, the key intermediate that was obtained by methylation with CF3SO3CH3 of the related zwitterionic unsymmetrical dye, with ammonia and methylamine, respectively. All three news dyes herein described displayed intense and narrow bands in the Vis/NIR region (693-714nm) and their singlet oxygen formation quantum yields ranged from 0.03 to 0.05. In vitro toxicity, in Caco-2 and HepG2 cells, indicated that dark toxicity was absent for concentrations up to 5µM (for the less active dye) or up to 1µM (for the two more active dyes). The three dyes present potential as photosensitizers, differing in irradiation conditions and period of incubation in the presence of irradiated dye. The less active dye needs a longer irradiation period to exhibit phototoxicity which is only evident after longer period of contact with cells (24h). However, the remaining two more active dyes produce higher phototoxicity, even at shorter incubation periods (1h), with shorter irradiation time (7min). Although in different extents, these dyes show promising in vitro results as photosensitizers.

Trichuris trichiura in a post-Colonial Brazilian mummy.

Trichuris trichiura is a soil-transmitted helminth which is prevalent in warm, moist, tropical and subtropical regions of the world with poor sanitation. Heavy whipworm can result either in Trichuris dysenteric syndrome - especially in children - or in a chronic colitis. In heavy infections, worms can spread proximally and may cause ileitis. Here we provide first microscopic evidence for a T. trichiura adult worm embedded in the rectum of a post-Colonial Brazilian adult mummy. During Colonial and post-Colonial times, many European chroniclers described a parasitic disease named Maculo whose symptomatology coincides with heavy helminthiasis. Based on our findings and on comparison of ancient textual evidence with modern description of heavy whipworm, we feel confident in considering that the two syndromes are expressions of the same pathological condition.

Photochemistry and Cytotoxicity Evaluation of Heptamethinecyanine Near Infrared (NIR) Dyes.

The present study investigates the photochemical properties of potential photosensitizers for photodynamic therapy, namely four commercial heptamethinecyanine dyes (IR125, IR780, IR813, IR820). Spectroscopic studies were made by means of laser induced fluorescence and laser flash photolysis in order to obtain fluorescence quantum yields and transient absorption spectra. Fluorescence lifetimes were also determined. The differences encountered were essentially related with the interaction of the sulfonate groups with the solvent, and also regarding the rigidification of the central bridge connecting the two nitrogen-containing heterocyclic groups. Transient absorption studies were performed both in aerated and oxygen free samples, to conclude about the formation of photoisomers and triplet state. For the four dyes under study, a cytotoxic evaluation in the dark and after irradiation was performed using HeLa cells as the model cell line, which revealed significant changes after irradiation mainly in IR125 and IR813 dyes. Confocal microscopy analysis showed that these dyes tend to enter to the intracellular space.

Photophysical studies of a new water soluble indocarbocyanine dye adsorbed onto microcrystalline cellulose and ß-cyclodextrin.

A water-soluble indocarbocyanine dye was synthesized and its photophysics were studied for the first time on two solid hosts, microcrystalline cellulose and b-cyclodextrin, as well as in homogeneous media. The inclusion of the indocarbocyanine moiety onto microcrystalline cellulose increased the dye aggregation with both H and J aggregates being formed. Adsorption on b-cyclodextrin enhanced aggregation in a similar way. The fluorescence quantum yields were determined for the powdered samples of the cyanine dye on the two hosts and a significant increase was observed relative to homogeneous solution. A remarkable concentration dependence was also detected in both cases. A lifetime distribution analysis has shown that the indocarbocyanine dye mainly occupies the amorphous part of cellulose and is not entrapped in the crystalline part of this host. In the b-CD case, the adsorption occurs outside the host cavity. In both hosts a strong concentration quenching effect is observed and only monomers emit. Both adsorptions may be explained by stereochemical constraints imposed by the two long sulphoethyl tails linked to nitrogen atoms of the indocarbocyanine dye.

Production of Blended Poly(acrylonitrile): Poly(ethylenedioxythiophene):Poly(styrene sulfonate) Electrospun Fibers for Neural Applications.

This study describes, for the first time, the successful incorporation of poly(ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) in Poly(acrylonitrile) (PAN) fibers. While electroconductive PEDOT:PSS is extremely challenging to electrospun into fibers. Therefore, PAN, a polymer easy to electrospun, was chosen as a carrier due to its biocompatibility and tunable chemical stability when cross-linked, particularly using strong acids. PAN:PEDOT:PSS blends, prepared from PEDOT:PSS Clevios PH1000, were electrospun into fibers (PH1000) with a diameter of 515 ± 120 nm, which after being thermally annealed (PH1000 24H) and treated with heated sulfuric acid (PH1000 H2SO4), resulted in fibers with diameters of 437 ± 109 and 940 ± 210 nm, respectively. The fibers obtained over the stepwise process were characterized through infra-red/Raman spectroscopy and cyclic voltammetry. The final fiber meshes showed enhanced electroconductivity (3.2 × 10-3 S cm-1, four-points-assay). Fiber meshes biocompatibility was evaluated using fibroblasts and neural stem cells (NSCs) following, respectively, the ISO10993 guidelines and standard adhesion/proliferation assay. NSCs cultured on PH1000 H2SO4 fibers presented normal morphology and high proliferation rates (0.37 day-1 vs. 0.16 day-1 for culture plate), indicating high biocompatibility for NSCs. Still, the low initial NSC adhesion of 7% calls for improving seeding methodologies. PAN:PEDOT:PSS fibers, here successful produced for the first time, have potential applications in neural tissue engineering and soft electronics.

9-Borafluoren-9-yl and diphenylboron tetracoordinate complexes of F- and Cl-substituted 8-quinolinolato ligands: synthesis, molecular and electronic structures, fluorescence and application in OLED devices.

Six new four-coordinate tetrahedral boron complexes, containing 9-borafluoren-9-yl and diphenylboron cores attached to orthogonal fluorine- and chlorine-substituted 8-quinolinolato ligand chromophores, have been synthesised, characterised, and applied as emitters in organic light-emitting diodes (OLEDs). An extensive steady-state and time-resolved photophysical study, in solution and in the solid state, resulted in the first-time report of delayed fluorescence (DF) in solid films of 8-quinolinolato boron complexes. The DF intensity dependence on excitation dose suggests that this emission originates from triplet-triplet annihilation (TTA). Density functional theory (DFT) and time-dependent density functional theory (TDDFT) studies give insight into the ground and excited state geometries, electronic structures, absorption energies, and singlet-triplet gaps in these new organoboron luminophores. Finally, given their highly luminescent behaviour, organic light-emitting diode (OLED) devices were produced using the synthesised organoboron compounds as emissive fluorescent dopants. The best OLED displays green-blue (λmaxEL = 489 nm) electroluminescence with an external quantum efficiency (EQE) of 3.3% and a maximum luminance of 6300 cd m-2.

Surface photochemistry: 3,3'-dialkylthia and selenocarbocyanine dyes adsorbed onto microcrystalline cellulose.

In this work, thia and selenocarbocyanines with n-alkyl chains of different length, namely with methyl, ethyl, propyl, hexyl and decyl substituents, were studied in homogeneous and heterogeneous media for comparison purposes. For both carbocyanine dyes adsorbed onto microcrystalline cellulose, a remarkable increase in the fluorescence quantum yields and lifetimes were detected, when compared with solution. Contrary to the solution behaviour, where the increase in the n-alkyl chains length increases to a certain extent the fluorescence emission Φ(F) and τ(F), on powdered solid samples a decrease of Φ(F) and τ(F) was observed. The use of an integrating sphere enabled us to obtain absolute Φ(F)'s for all the powdered samples. The main difference for liquid homogeneous samples is that the increase of the alkyl chain strongly decreases the Φ(F) values, both for thiacarbocyanines and selenocarbocyanines. A lifetime distribution analysis for the fluorescence of these dyes adsorbed onto microcrystalline cellulose, evidenced location on the ordered and crystalline part of the substrate, as well as on the more disordered region where the lifetime is smaller. The increase of the n-alkyl chains length decreases the photoisomer emission for the dyes adsorbed onto microcrystalline cellulose, as detected for high fluences of the laser excitation, for most samples.

Color and luminescence stability of selected dental materials in vitro.

PURPOSE: To study luminescence, reflectance, and color stability of dental composites and ceramics. MATERIALS AND METHODS: IPS e.max, IPS Classic, Gradia, and Sinfony materials were tested, both unpolished (as-cast) and polished specimens. Coffee, tea, red wine, and distilled water (control) were used as staining drinks. Disk-shaped specimens were soaked in the staining drinks for up to 5 days. Color was measured by a colorimeter. Fluorescence was recorded using a spectrofluorometer, in the front-face geometry. Time-resolved fluorescence spectra were recorded using a laser nanosecond spectrofluorometer. RESULTS: The exposure of the examined dental materials to staining drinks caused changes in color of the composites and ceramics, with the polished specimens exhibiting significantly lower color changes as compared to unpolished specimens. Composites exhibited lower color stability as compared to ceramic materials. Water also caused perceptible color changes in most materials. The materials tested demonstrated significantly different initial luminescence intensities. Upon exposure to staining drinks, luminescence became weaker by up to 40%, dependent on the drink and the material. Time-resolved luminescence spectra exhibited some red shift of the emission band at longer times, with the lifetimes in the range of tens of nanoseconds. CONCLUSIONS: Unpolished specimens with a more developed surface have lower color stability. Specimens stored in water develop some changes in their visual appearance. The presently proposed methods are effective in evaluating the luminescence of dental materials. Luminescence needs to be tested in addition to color, as the two characteristics are uncorrelated. It is important to further improve the color and luminescence stability of dental materials.

Red and Near-Infrared Absorbing DicyanomethyleneSquaraine Cyanine Dyes: PhotophysicochemicalProperties and Anti-Tumor Photosensitizing Effects.

Photodynamic therapy is a medical modality developed for the treatment of several diseases of oncological and non-oncological etiology that requires the presence of a photosensitizer, light and molecular oxygen, which combined will trigger physicochemical reactions responsible for reactive oxygen species production. Given the scarcity of photosensitizers that exhibit desirable characteristics for its potential application in this therapeutic strategy, the main aims of this work were the study of the photophysical and photochemical properties and the photobiological activity of several dicyanomethylene squaraine cyanine dyes. Thus, herein, the study of their aggregation character, photobleaching and singlet oxygen production ability, and the further application of the previously synthesized dyes in Caco-2 and HepG2 cancer cell lines, to evaluate their phototherapeutic effects, are described. Dicyanomethylene squaraine dyes exhibited moderate light-stability and, despite the low singlet oxygen quantum yields, were a core of dyes that exhibited relevant in vitro photodynamic activity, as there was an evident increase in the toxicity of some of the tested dyes exclusive to radiation treatments.

In vitro phototherapeutic effects of indolenine-based mono- and dithiosquaraine cyanine dyes against Caco-2 and HepG2 human cancer cell lines.

Photodynamic therapy is a noninvasive approach for the treatment of oncological and nononcological diseases which has attempted to address the shortcomings and disadvantages of conventional cancer therapies. Given the scarcity of photosensitizers that exhibit desirable characteristics for its potential application in this therapeutic strategy, the main aims of this work were the study of the photophysical and photochemical properties, and the in vitro photobiological activity of several squaraine cyanine dyes. Thus, herein, the synthesis of indolenine-based N-methyl and N-ethyl mono- and dithiosquaraine dyes, the study of their spectroscopical properties, aggregation behavior, photodegradation and singlet oxygen production ability, and the further application of the previously synthesized dyes in colorectal adenocarninoma and hepatocellular carcinoma cell lines to evaluate their phototherapeutic effects, are described. Thionation significantly favored the ability to singlet oxygen production, and moderate photostability was observed for squaraine and monothionated dyes. Squaraine and monothiosquaraine cyanine dyes showed high promise within the tested concentration range regarding their potential application as cancer photodynamic therapy photosensitizers. Squaraine dyes' monothionation resulted in the preparation of compounds with poor photocytotoxicity, which was an undesirable effect on their phototherapeutic application.

Photochemical /Photocytotoxicity Studies of New Tetrapyrrolic Structures as Potential Candidates for Cancer Theranostics.

BACKGROUND: Detailed photochemical and photocytotoxicity studies of two new porphyrins: 5,10,15,20-meso-tetrakis-(4-acetoxy-3-methoxyphenyl) porphyrin (P2.1) and 5-(4-hydroxy-3- methoxyphenyl)-10,15,20-tris-(4-acetoxy-3-methoxyphenyl)porphyrin (P2.2) are reported, as potential candidates for theranostics. For powdered samples of P2.1 and P2.2 adsorbed onto a powdered biocompatible substrate, polyethylene glycol (PEG), a concentration study was performed, correlating the fluorescence emission intensity with sample absorption to determine the useful concentration range for photodynamic therapy of cancer (PDT) in which aggregation does not occur. Cytotoxicity studies were performed in dark and illuminated conditions. METHODS: The laser induced luminescence set-up is home-made, a N2 laser is used as the excitation source and a time gated charged-coupled device (ICCD) as the detector. Fluorescence lifetime determinations were made using pulsed light sources from the excitation LEDs and measures of the fluorescence intensities at different time delays after the excitation pulse. The singlet oxygen formation quantum yields ΦΔ measurements were obtained by comparing the total area of the emission spectra for the reference compound and also for the samples under study in the same solvent and with the same optical density at the excitation wavelength (405 nm). An integrating sphere for relative and absolute measurements was used in this work as an alternative methodology to obtain the values for the fluorescence emission quantum yields (ΦF) of the adsorbed porphyrin under study. The cytotoxicity evaluation was made in the dark and under irradiation, using four different human tumor cell lines and one non-tumor primary cell culture. RESULTS: In order to establish the useful range of concentrations of the sensitizer for PDT, and due to the use of powdered samples, a special methodology was needed: the variations of the fluorescence lifetimes and fluorescence quantum yields were evaluated as a function of the concentration of the dye, measured by (1-R)*fdye. Both ΦF and τF are constant in the range from 0.002 to about 0.050 µmol g-1, and only after that a concentration quenching effect becomes visible, decreasing both ΦF and τF. This methodology is based in the correlations established between the Remission Function values and ΦF and τF obtained for increasing values of the sensitizer concentrations. CONCLUSIONS: The study of the aggregation effects of P2.1 and P2.2 porphyrins into a PEG matrix allowed us to determine the usable concentration range for photodynamic therapy use, where the aggregation of porphyrins decreases, therefore reducing the PDT action. The use of an integrating sphere for relative and absolute measurements of fluorescence quantum yields and also the lifetime studies as a function of the dye loading confirms the useful range for the use of P2.1 and P2.2 in PEG as powdered samples. The determination of the GI50, the porphyrin concentration which inhibits 50% of the cell growth, evidences that P2.2, the A3B porphyrin overtakes P2.1 (the A4 porphyrin) in terms of PDT efficiency and both porphyrins are much better PDT agents than the unsubstituted porphyrin, TPP. These data clearly show that porphyrins P2.2 and P2.1 exhibit an excellent behaviour in terms of its photocytotoxicity. These results encourage us to pursuit in the study of this family of porphyrins in which a balance of hydrophobic versus hydrophilic substituents in the phenyl group was achieved.

Emerging Therapeutic Targets in Oncologic Photodynamic Therapy.

BACKGROUND: Reactive oxygen species sustain tumorigenesis and cancer progression through deregulated redox signalling which also sensitizes cancer cells to therapy. Photodynamic therapy (PDT) is a promising anti-cancer therapy based on a provoked singlet oxygen burst, exhibiting a better toxicological profile than chemo- and radiotherapy. Important gaps in the knowledge on underlining molecular mechanisms impede on its translation towards clinical applications. AIMS AND METHODS: The main objective of this review is to critically analyse the knowledge lately gained on therapeutic targets related to redox and inflammatory networks underlining PDT and its outcome in terms of cell death and resistance to therapy. Emerging therapeutic targets and pharmaceutical tools will be documented based on the identified molecular background of PDT. RESULTS: Cellular responses and molecular networks in cancer cells exposed to the PDT-triggered singlet oxygen burst and the associated stresses are analysed using a systems medicine approach, addressing both cell death and repair mechanisms. In the context of immunogenic cell death, therapeutic tools for boosting anti-tumor immunity will be outlined. Finally, the transcription factor NRF2, which is a major coordinator of cytoprotective responses, is presented as a promising pharmacologic target for developing co-therapies designed to increase PDT efficacy. CONCLUSION: There is an urgent need to perform in-depth molecular investigations in the field of PDT and to correlate them with clinical data through a systems medicine approach for highlighting the complex biological signature of PDT. This will definitely guide translation of PDT to clinic and the development of new therapeutic strategies aimed at improving PDT.

Surface photochemistry: organic molecules within nanocavities of calixarenes.

In order to gain more information regarding photochemical processes in heterogeneous environments (opaque or powdered samples) laser induced time resolved luminescence and diffuse reflectance transient absorption spectroscopies were used for the study of benzophenone (and other neutral organic molecules) as guests and p-tert-butylcalix[n]arenes with n = 4, 6 and 8 (H(n)CLX[n]) and partially or totally O-propylated p-tert-butylcalix[4]arenes (H(n)Pr(m)CLX[4], n = 2, 1 and 0; m = 2, 3 and 4, respectively) were used as hosts. One of the main conclusions was that the solid support can deeply affect or even control the photochemistry of an adsorbed probe. A simple new methodology for lifetime distribution analysis of the decay of the probes included into calixarenes and other nanocavities was applied with success for decay data obtained with the use of intensified charge couple devices, i.e. intensified charge couple devices, ICCDs. Diffuse reflectance laser flash photolysis and gas chromatography - mass spectrometry techniques also provided complementary information, the former about transient species and the latter regarding the final products formed after light absorption.

Facile functionalization of cotton with nanostructured silver/titania for visible-light plasmonic photocatalysis.

In the present work, a simple, reliable and cost-effective approach to functionalize cotton fabrics with Ag-TiO2 nanoparticles strongly bound to the fibres and with visible-light-responsive photo-activity is presented. The hybrid cotton-Ag-TiO2 fabrics were characterized by Raman, AFM, FE-SEM, TGA, XPS GSDR, and LIL to confirm the generation of metallic Ag nanoparticles and crystalline TiO2 and investigate how the concentration of Ag and TiO2 precursors affected the morphology and the luminescence properties of the nanostructured layer grafted on the cotton fibres. The photocatalytic activity of the cotton-Ag-TiO2 hybrid systems was evaluated by the discoloration of Remazol Brilliant Blue R in water under a xenon lamp irradiation (sunlight simulator) equipped with selective filters. The extended photocatalytic activity to the visible is here explained by a synergistic effect of both the excitation of the Ag NPs plasmon resonance by visible light and a delayed electron-hole recombination rate caused by Ag NPs, as it can be observed by UV absorption.

Luminescence lifetime distributions analysis in heterogeneous systems by the use of Excel's Solver.

A detailed study of the luminescence decay curves of pyrene included within p-tert-butylcalix[4]arene cavities and benzophenone into silicalite channels is reported. A new methodology for a lifetime distribution analysis of the decay curve of probes onto heterogeneous surfaces is presented, which allows for asymmetric distributions and uses Voigt profiles (Gaussian and Lorentzian mixture) instead of pure Gaussian or Lorentzian distributions. Our approach uses a very simple and widely available tool for fitting, the Microsoft Excel Solver. In the case of the pyrene/tert-butylcalix[4]arene sample, the room temperature luminescence detected in the microsecond time scale was not only the phosphorescence of pyrene but also monomer delayed fluorescence, crystal phosphorescence, and excimer delayed fluorescence. In the benzophenone/silicalite case, three emissive forms of benzophenone could be assigned, one of benzophenone included into the silicalite circular zigzag channels, another for emplacement into the elliptical straight channels and finally when benzophenone is placed at the crossing points of those silicalite channels, where smaller spatial restrictions for benzophenone exist.

Comprehensive photochemistry and photophysics of land- and marine-based beta-carbolines employing time-resolved emission and flash transient spectroscopy.

The photophysical and photochemical behavior of Norharmane (Norh), Harmane (Hara) and Harmine (Hari) and their cations have been examined as a function of the nature of the solvent. Time-resolved emission in nonprotic polar solvents showed fluorescence for all and also phosphorescence for Hari. All emissions were assigned as those of the neutral molecules. Norh and Hari showed fluorescence of both the neutral and the cation in methanol as well as phosphorescence of the neutral while Hari also had fluorescence of the zwitter ion. In ethanol, Norh and Hari displayed fluorescence and phosphorescence of the neutral. The ground-state cations of Norh and Hari exhibited fluorescences of the cation and Hari also had a phosphorescence (cation). The flash transient spectra in nonprotic solvents of all three carbolines had long-lived triplet transients only of the neutral. Triplet and singlet oxygen yields were quite high, 0.31-0.40. Direct excitation of any of the cations gave only the cation triplet. The triplet yields of the cations appear to be low (0.01-0.10 range). Theoretical calculations were done relative to location of triplet states. Some new information will be reported on other naturally occurring differently substituted marine-based beta-carbolines. The impact of all of the foregoing observations on the photosensitizing potential of all compounds is discussed.